1. Field of the Invention
This invention relates to chemical mechanical planarization or polishing tools. More particularly, the invention relates to the supply of slurry.
2. Description of the Prior Art
Chemical mechanical polishing (CMP) for planarization of semiconductor wafers is widely used in the manufacture of integrated circuits (IC's). CMP differs from straight mechanical polishing by virtue of the fact that a chemical etchant is supplied at the same time. Said etchant does not fully dissolve the surface but instead produces a layer of low mechanical integrity that is easily removed with fine abrasive. This eliminates the need for using a series of decreasing slurry size particles as is commonly done in mechanical polishing.
For example U.S. Pat. No. 3,615,955 (Regh et al.) discloses the use of a container with a restricted opening held over the center of the rotating platen. The distribution of the slurry across the pad is left to centrifugal forces. U.S. Pat. No. 5,492,594 (Burke et al.) shows a slurry dispenser and a dispensing arm supplying slurry somewhere between the center and rim of the pad/platen. Again the distribution of the slurry across the pad is left to centrifugal forces. U.S. Pat. No. 5,246,525 (Sato) describes a system where slurry is distributed through the platen and exits through a plurality of supply ports concentrically located on the pad in various arrangements and with independent slurry supply means. Use of three independent slurry supply means make the method more expensive and therefore the cost of wafer production is greater.